Simple Pendulum

Made of a mass m and a string or rod of length L

Harmonic Motion because of the restoring force that pulls it back towards equilibrium.

WHere does the restoring force come from?

the sin component of weight

Depends on neither mass or amplitude

depends strictly on length and the force of gravity

 $T=2\pi\sqrt{\frac{L}{g}}$  

Many things run only because of driven oscillations( cycles cause by an outside force.

Natural frequency- frequency an object oscillates by itself

A system driven at its natural frequency is in resonance- they will often have large amplitudes

The resonance of objects effects how they are built- materials science is very important for engineering